Dragging front factory disc brakes and metering valve.

[miller]

Probably nothing, but I've read the correct brake fluid needs to be used. That's for the dragging disc brakes. Wrong fluid would heat up, expand, and not release properly.

What's the history on the master? One 'rebuilt' master I got my hands on, was put together wrong. If it's original, I'd consider, with a good break-down drawing of it, to operate on it. Their easy to take apart, look parts over, check the bores condition, and new seals.
Rear brakes...drum, right? Getting brake fluid to the wheel cylinders okay?

Answer is there! Just have to look deep enough.

 

[AR67GTX]

Miller - I think he is using DOT 3 fluid - might be 4. It's not silicone.

Yes, I was tempted to pull the master and take it apart but we were out of time. He brought the Hemi-specific booster from a specialty rebuilder and they sourced the master cylinder also. He was going to call Tony's on a replacement.

Rear brakes have been bled a couple of times and we had the drums off of them a few weeks ago to re-install the retractor spring that came off. It has a bend in the straight part on one end to clear around the adjustor spool and it had been installed such that it was stretched across the spool and it finally kicked it loose. But anyway, brakes were checked we put back together and the parking brake adjusted and they worked good.

Calipers are the 4 piston Bendix type so a random piston dragging would probably not lock them up completely like a single piston, slider type might.

 

[miller]

I think he is using DOT 3 fluid - might be 4. It's not silicone.

Okay. Can't tell you for sure. I've seen write-ups, on the various brake fluids, and which systems to use each for. Should say on the container. On mine, old school conversion, single piston pin type calipers, using Valvoline 3+4 synthetic. I don't usually use synthetic anything, but thought I'd give it a shot. So far, good.

Calipers are the 4 piston Bendix type so a random piston dragging would probably not lock them up completely like a single piston, slider type might.

Well, mine has only one piston that can hang...his has four. Only takes one to gum up the works, as far as dragging. Each of the four pistons/bores would have to be in good shape. I'm sure they work great, as long as they are in good shape.

He was going to call Tony's on a replacement.

Yeah, that might be the best bet.
I'd dang sure pull the old master down, for a look-see, just to know what's going on. Unless, he has to turn it in as a core.
As simple as most of those masters are, surprising, the simplest thing can mess them up.
Good luck on it! Fingers crossed!! (I know they can be a PITA.)

 

[miller]

Rear drum brakes. Self-adjusting, or no?
Either way, guess you know, they probably need to be manually adjusted, to the drums. Even the self-adjusted. Self-adjusted a little harder, since the adjusting tab has to be 'held off' the adjuster wheel, when doing it manually. It will show in the book.

 

[AR67GTX]

Yes - they are self-adjusting. They may need some more adjusting but they were applying immediately after we put the spring and drum back on and tried them. And they applied when we finally started the motor up last weekend. A mystery.

 

[miller]

Yes - they are self-adjusting.

Again, probably already know.
Self-adjusting, the adjuster 'teeth' are fine. Manual adjust are coarse. And, either one, there's a right-side, left-side adjusters, installed correct direction.
On those self-adjusters, think it's normal when manually adjusting them, to tighten until the wheel is hard to rotate. Then, same on each side, back off same # of clicks, until no drag.

 

[AR67GTX]

I was not there when the rear brakes were originally assembled (not that that would have been any guarantee on proper install). I studied them some against the shop manual the other day and except for the one retraction spring it looked good. Of course the manual only shows a front and rear right side set up and they figure I guess that the left side should be intuitive. I did notice that the self-adjuster cables did not seem taunt and one time it actually had slipped out of the groove in the guide. The rear brakes are probably something we need to look at again as it wouldn't be the first thing that has ended up installed backwards on this car. Right now though the front brakes are the biggest issue. Last communication was he was talking to someone named Pirate Jack Brakes (?) who suggested replacing the valve with an OE valve (not first to suggest that). Also to disconnect the line outlets and make sure we have flow - but we bled the brakes and had flow. I'm not sure what I should expect out of Pirate Jack.

​

 

[miller]

Of course the manual only shows a front and rear right side set up and they figure I guess that the left side should be intuitive.

Yep, book shows the one side, on the opposite side it's simply 'backwards' from the photo.
I had to laugh! I've got a 67 8 3/4" rear on my 64, and tripped over the needed parts to install 11 x 3" drum brakes (police). Awhile back, had to pull the rear wheels and drums...and noticed on one side, I had put the brake shoes on backwards!
Short shoe goes to the front. DUH!

I did notice that the self-adjuster cables did not seem taunt and one time it actually had slipped out of the groove in the guide.

Those cables should be taunt, so, some little part not mounted right?? If it was mine, I'd pull both drums, look things over, and fix what needs fixing. IF something is wrong, it will only make trouble later.

Right now though the front brakes are the biggest issue.

On mine, 13 1/2" disc, though single piston pin-type, should be pretty simple. Book should show each piece involved, added valves and such.
Of course, on the dual pot master, biggie goes to the front disc. A bit of a pain, to check any factory included valves, between the master, and calipers. Pretty sure he wants to keep everything stock, considering the car.
Brake pads dragging...is that the problem? Have the rotors ever been touched, meaning cut.
Besides the caliper pistons not returning, or a problem with any added valves, sometimes the rotors can get 'hard spots'. But, that would give a skipping effect on those brakes.

 

[AR67GTX]

Turns out Pirate Jack is a mostly a Chevrolet specialists but just so happens they have a Mopar specialist on the staff who seems to know the cars pretty well. He said, yeah - the metering valves are junk but the proportioning valves are usually not an issue. He suspected the rod to the master cylinder was too long. He is sending a new MC and in the meantime he removed the old one today and we spent awhile checking things.

We checked the booster push rod length and the only reference in the shop manual was for a Midland single diaphragm booster and rod protrusion is .91 to .92". His booster is a dual diaphragm Bendix and measures about .85" to .86" with engine off and .88" with engine on and vacuum to the booster.

Lightly applying and releasing the brakes resulted in the pushrod behaving normally (out and back in).

We took the MC apart and it looked fine. The compensating port would be uncovered by the piston seal by about .08" with no brake pressure so release of line pressure would not appear to be an issue. Even if he extends the rod length to about .91" he will still have about .04 - .05 of clearance on the compensation port. But I don't see how we gain anything on this problem by doing that. His brake pedal doesn't have any noticeable free play at top of pedal and seems to immediately apply the brakes when barely depressed.

The rear piston doesn't hang up and the bore and seals look fine. The spring retaining screw on the rear piston was barely engaged as evidenced by it eventually and surprisingly came loose and the spring and piston flew all over my garage. I noticed the front piston does take it's time moving back when pressure against it is released (a second or two) but that may be the residual valve for the drum brakes and we aren't noticing a pressure release issue with them.

He was going to get back with Pirate Jack's tech guy tomorrow and see what he thought about our findings on the push rod. Hoping the new MC arrives on Friday.

 

[miller]

His brake pedal doesn't have any noticeable free play at top of pedal and seems to immediately apply the brakes when barely depressed.

Hmmm. I'm far from an expert on these things. But, I'd have to think at least 'some' free play would be needed. Might be worth checking. Whole reason, in the MC, there's a stop for the movement of the pistons.
(That could also be why the discs are dragging.)

 

[AR67GTX]

Installed a new MC today and shortened the pushrod as short as it would go. Everything seemed to be working after that - about 1 to 1- 1/2" free movement of the brake before it starts to firm up but still gets hard well above the floor. Not sure if something in the other MC we just weren't seeing or if it was just the pushrod being adjusted out so far. I suspect the pushrod adjustment for the Bendix booster is different than shown for the other one in the service manual.

 

[Dragon Slayer]

Glad you got it, but a 69 Factory Brake car had the Bendix 4 piston caliper for a B body. There would be no metering valve. Just the distribution block with warning light, and proportioning valve for rear. The Disc MC should NOT have a residual pressure check valve in the front. Just rear. If he was using reproduction stuff, who knows what was holding that pressure in, but if the internal pistons of the MC where not set correctly to uncover the compensation port in the MC, the front pressure would have remained until it bleed off by leak by. Or maybe it was a drum drum type that had a residual valve in the front too.

 

[AR67GTX]

He has the 4-piston Bendix brake calipers. That's the first time anyone has said it should not have a metering valve though. It shows one in the service manual although it shows a bit different mount location for it than the mount for the current replacement one. We assume only the front chamber (rear brakes) part of the MC has a residual valve but without pulling the seat we can't confirm it.

 

[dadsbee]

My understanding is that the metering valve was installed for single piston Kelsey/Hayes calipers in late '69 / 70 for roadrunners/Birds etc... my car has them and the valve on it.

 

[Dragon Slayer]

In Model year 69 and earlier, B bodies used the Bendix 4 caliper with no meter valve. A bodies used a 4 piston KH FIXED set up, no meter valve. I rechecked my Dart, Coronet Charger 69 service manual and I did not see reference to Meter valve, just proportioning valve which is used to reduce pressure to rear brakes. But the Plymouth 69 service manual covered A/B and C so you have to follow the sections to the specific brake type.

69 changed brakes for C body, going to the Kelsey Hayes Floating Caliper single piston and used the metering valve in that set up. But C body only. Look at the specification section and you see the rotor was 11.75" for the 69 KH floating caliper brake set up. 69 B used a 11.19"rotor, and in 70 when they moved to the floating Caliper for B and E body the rotor was 10.98".

1970 introduced the KH single piston Floating Caliper set up for B and E body. Changed the disc, and caliper and added caliper bracket with a new spindle. This was a 70-72 setup for both body styles and added the metering valve. Early 70 cars have the 3 piece valve set up. Distribution block, Meter valve and proportioning valve. Later in the year they moved to a combined 2 valve set up, but you still had metering, and proportioning for the Disc set up.

 

[AR67GTX]

I'll pass that on to him and let him research his stuff. He bought all the restoration guides, assembly manuals and shop manuals for the car. Right now it does seem to be working so probably leave well enough alone at the moment.

Unfortunately we heard some sort of bang in the rear when we test drove it - like something rolling in the trunk. When he got to the monthly cruise night Friday he discovered he doesn't have parking brakes any longer. So I guess next week we will go back through the rear brakes and see what came apart back there.

Thanks Dragon Slayer